1. Field of the Invention
The present invention relates to a low fire-spreading cigarette, when lit, a burning part of which does not easily spread fire to surrounding objects, thus preventing a fire that might be caused by accident due to a smoker's carelessness or the like.
2. Description of the Related Art
In order to prevent the burning part of a cigarette from spreading a fire, for example, when the cigarette is dropped by the smoker by accident due to carelessness onto a floor or the like, there have been proposed a cigarette imparted with a self-extinguishing property by providing its wrapper paper with a cellulose paper band having a width of 2 to 20 mm (Jpn. Pat. Appln. KOKAI Publication No. 63-85200) and a cigarette provided with a band coated with a flame-retarding substance on the tobacco wrapper paper (see Jpn. Pat. Appln. KOKAI Publication No. 7-300795). Further, a tobacco wrapper paper to which an incombustible material is attached is conventionally known. These techniques are based on the findings that when high and low combustible regions are made in a tobacco wrapper paper sheet, ordinary smoking can be conducted in the highly combustible region, whereas the cigarette extinguishes by itself when there is a substance in contact with the cigarette in the low combustible region.
In the meantime, it is conventionally known well that if the burning rate of a cigarette is lowered in order to reduce the amount of sidestream smoke per unit time, a cigarette that easily extinguishes by itself can be provided. An example of such a cigarette is the one using wrapper paper having a small amount of filler blended thereinto as an inside wrapper and a conventional wrapper paper as an outside wrapper paper sheet, to wrap shredded tobacco. (See the specification of Japanese Patent No. 2572488.)
However, in the case where wrapper paper having an incombustible region is used, a highly combustible portion and a low combustible portion are created. Due to this, some unnatural suction may become necessary during smoking, and the taste of the smoke may vary. Further, the method in which a self-extinguishing property (low fire-spreading property) is imparted by reducing the burning rate is conventionally realized by reducing the air permeability of the wrapper paper. Thus, the ventilation effect of the wrapper paper is deteriorated, thereby causing a change in the smoking taste. Therefore, ordinary smokers may feel odd while smoking. In order to prevent the adverse effect of lowered ventilation caused by the reduction of the air permeability of the wrapper paper, a method of is also known, in which a filter is attached to a cigarette and perforations are made in its filter tipping paper as a compensation for the ventilation. However, perforation on filter tipping paper is a costly process.
On the other hand, Jpn Pat. Appln. KOKAI Publication No. 60-59199 discloses a technique of packaging a tobacco column with two packaging members each having a predetermined range of BMI (burn rate index) value, in order to provide a smoking article having a low tendency. Of the two packaging members, the inner member has an air permeability of low as 1 CORESTA unit. At any event, Jpn Pat. Appln. KOKAI Publication No. 60-59199 does not discloses or even suggest that the heat conductivity of wrapper paper is correlated to the fire spreading property of cigarette.
An object of the present invention is to provide a low fire-spreading cigarette having the same burning rate in its axial direction as that of a conventional cigarette.